1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that includes a liquid crystal layer divided into a plurality of domains in which the alignments (i.e., tilt angles) of liquid crystal molecules are controlled.
2. Description of the Related Art
Liquid crystal display devices are light, thin and of low power consumption, and hence are used in various machines, such as OA devices, information terminals, clocks and TV sets. In particular, active matrix type liquid crystal display devices provide excellent responsiveness by switching pixels using thin-film transistors (TFTs), therefore can be used as the display monitors of cellular phones, TV sets and computers that are required to display a large number of image information items.
In recent years, in accordance with an increase in the amount of information, there is a demand for increases in the degree of definition and display speed. Definition can be enhanced by miniaturizing a TFT array structure to increase the number of pixels employed therein. Further, concerning enhancement of display speed, to shift the alignment of liquid crystal molecules in a shorter time, a liquid crystal display mode is required in which a molecule response speed twice to several tens of times the present response speed can be acquired. As the liquid crystal display mode, the OCB type, VAN type, HAN type, π-alignment type, which utilize nematic liquid crystal, surface stabilized ferroelectric liquid crystal type utilizing smetic liquid crystal, or anti-ferroelectric liquid crystal type can be used.
In particular, attention has now been paid to the VAN-type alignment mode, since it exhibits a higher response speed than the conventional twist nematic (TN) type alignment mode, and does not require the conventional rubbing alignment process that may well cause defectiveness such as electrostatic breakdown. Further, the VAN-type alignment mode is also advantageous in designs for viewing angle compensation can be easily achieved. A wide viewing angle can be acquired by employing a multi-domain format, in which each pixel is divided into a plurality of domains between which the alignment of liquid crystal molecules differs.
Jpn. Pat. Appln. KOKAI Publication No. 6-43461, for instance, discloses a liquid crystal display device having a structure (a cutout portion), which serves as means for controlling the alignments of liquid crystal molecules, and in which a part or periphery of an electrode is electrically disconnected. In this liquid crystal display device, a change in electric field applied between the substrates is caused by a cutout portion or near this portion, which uniquely determines the tilt corresponding to the dielectric anisotropy of the material of the liquid crystal molecules.
However, if each pixel is divided into a plurality of domains by dielectric layers on the electrodes, or by slits formed in the electrodes, the light transmissivity of the dielectric layer or the portion with the slit may well be reduced because of light loss.
Further, in recent years, there is a demand for a super definition liquid crystal display in which the width of each pixel electrode is about 40 μm or less. If in such a super definition liquid crystal display, the conventional dielectric layers or slits are utilized, the light transmissivity will be significantly reduced.